396976 ÷ 21 
The aim is to understand the frequency of 21 in 396976.

On to step 1:
21 goes into 3 0 times with a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 3 after subtracting 0 from 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 21

Advancing to step 2:
The number 21 fits into 39 1 times, leaving a remainder of 18.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we take 21 away from 39, we end up with 18.
Grab the next digit (6) from the dividend, add it to 18, then carry on: 186 / 21

Advancing to step 3:
If we divide 186 by 21, we get 8 and a remainder of 18.
Put 8 as the next digit of the answer. 
Result so far: 18.0
If we take 168 away from 186, we end up with 18.
Append the next digit (9) from the dividend to 18 and continue with: 189 / 21

Advancing to step 4:
189 divided by 21 is 9 with a remainder of 0.
Record the quotient 9 as the next digit in the result. 
Result so far: 189.0
If we subtract 189 from 189, we get 0.
Grab the next digit (7) from the dividend, add it to 0, then carry on: 7 / 21

Let's proceed to step 5:
21 can be fit into 7 0 times, resulting in a remainder of 7.
Record the quotient 0 as the next digit in the result. 
Result so far: 1890.0
If we subtract 0 from 7, we get 7.
Include the next digit (6) from the dividend after 7, then repeat: 76 / 21

Advancing to step 6:
If we divide 76 by 21, we get 3 and a remainder of 13.
Use 3 as the next digit of our solution. 
Result so far: 18903.0
If we take 63 away from 76, we end up with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 7:
130 divided by 21 is 6 with a remainder of 4.
Use 6 as the next digit of our solution. 
Result so far: 18903.6
The remainder is 4 after subtracting 126 from 130.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 8:
21 goes into 40 1 times with a remainder of 19.
The next digit of our result is 1. 
Result so far: 18903.61
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Let's proceed to step 9:
The number 21 fits into 190 9 times, leaving a remainder of 1.
Write down 9 as next digit of the result. 
Result so far: 18903.619
The remainder is 1 after subtracting 189 from 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Step 10:
21 goes into 10 0 times with a remainder of 10.
The next digit of our result is 0. 
Result so far: 18903.619
Deduct 0 from 10 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 11:
100 divided by 21 is 4 with a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 18903.61904
If we take 84 away from 100, we end up with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Advancing to step 12:
21 can be fit into 160 7 times, resulting in a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 18903.619047
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 13:
21 can be fit into 130 6 times, resulting in a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 18903.6190476
Deduct 126 from 130 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 14:
21 can be fit into 40 1 times, resulting in a remainder of 19.
Record the quotient 1 as the next digit in the result. 
Result so far: 18903.61904761
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

The final result is 18903.61904761 with a remainder of 1.9e-08.